The invention relates to a medical device for determining the position of intracorporeal implants such as fixation systems, plates or the like.
In the medical treatment of spinal fractures, for example, which can be caused by falls, osteoporosis, tumors, etc., various kinds of fixation systems are used in which screws with an eyelet, referred to as pedicle screws, are used, the fixation rods being inserted through their respective eyelets.
In the conventional operating procedure, the pedicle screws and fixation rods are introduced by detaching large areas of the muscles from the spinal column, the pedicle screws being screwed into the vertebral body of the spinal column on both sides of the vertebral canal, and the fixation rods being inserted from the top downward through the eyelets of the pedicle screws.
In young patients, the fixation rods are removed after about six months, since otherwise there is a danger of the screws/rods breaking with the increasing mobility of the patient.
In older patients, for example with osteoporotic damage (fractures, sintering) of the spinal column, permanent fusion is often generally carried out by treatment with a rod system (internal fixator, optionally in combination with bone cement) or a plate system according to the fixator principle. However, there is a danger here of the screws breaking through into the intervertebral disc space because of the reduced bone strength in osteoporosis.
By contrast, in the so-called minimally invasive method, the spinal column is not exposed, and instead the treatment is performed from the outside, only through small incisions in the skin. This method includes, for example, vertebroplasty, in which bone cement is injected into the vertebral bodies without these being straightened beforehand, or kyphoplasty, in which collapsed vertebrae are straightened with the aid of an inflatable balloon and then with injected biological cement. By contrast, the introduction of fixation rods in the treatment of fractures of the vertebral bodies has not hitherto been possible by a minimally invasive procedure.
The object of the invention is to make it possible to determine the position of intracorporeal implants in a simple way, without the need for major surgical procedures.